Steady-state pleural fluid flow and pressure and the effects of lung buoyancy

Management of Chest Drains After Thoracic Resections

Immediately after lung resection, air tends to collect in the retrosternal part of the chest wall (in supine position), and fluids in its lower part (costodiaphragmatic sinus). Several general thoracic surgery textbooks currently recommend the placement of 2 chest tubes after major pulmonary resections, one anteriorly, to remove air, and another into the posterior and basilar region, to drain fluids. Recently, several authors advocated the placement of a single chest tube. In terms of air and fluid drainage, this technique demonstrated to be as effective as the conventional one after wedge resection or uncomplicated lobectomy.

Pleural mechanics and fluid exchange

The pleural space separating the lung and chest wall of mammals contains a small amount of liquid that lubricates the pleural surfaces during breathing. Recent studies have pointed to a conceptual understanding of the pleural space that is different from the one advocated some 30 years ago in this journal. The fundamental concept is that pleural surface pressure, the result of the opposing recoils of the lung and chest wall, is the major determinant of the pressure in the pleural liquid. Pleural liquid is not in hydrostatic equilibrium because the vertical gradient in pleural liquid pressure, determined by the vertical gradient in pleural surface pressure, does not equal the hydrostatic gradient. As a result, a viscous flow of pleural liquid occurs in the pleural space. Ventilatory and cardiogenic motions serve to redistribute pleural liquid and minimize contact between the pleural surfaces. Pleural liquid is a microvascular filtrate from parietal pleural capillaries in the chest wall. Homeostasis in pleural liquid volume is achieved by an adjustment of the pleural liquid thickness to the filtration rate that is matched by an outflow via lymphatic stomata.

On computational control of flow in airblast atomisers for pulmonary drug delivery

Among different approaches to successful pharmacotherapy the pulmonary drug delivery (PDD) mode plays an increasingly important role. In this paper PDD systems based on air-blast atomisation have been analysed mathematically. In order to allow the bioengineer to estimate the degree of effectiveness of a specific system prototype and to lay the basic principles for design, a conservation-law-based mathematical model is discussed. Key control parameters that allow improvement in the efficiency of the system have been identified and main characteristics of the system have been analysed numerically as functions of these parameters.